The present invention relates generally to squeezable containers which are formed of two or more layers of different materials. More particularly, the present invention is directed to a multilayered, squeezable, structurally self-supporting container which is capable of dispensing a controlled amount of product.
Certain adhesives, such as those which contain a volatile component, must be housed in a container which prevents moisture and oxygen ingress into the container, and egress of the volatile component of the adhesive out of the container. It is important to provide a container which can control both ingress and egress, because either one will typically be detrimental to the adhesive housed within the container, or the container itself.
For example, cyanoacrylate adhesives are adversely affected by moisture, and exposure to such will cause the adhesive to begin to xe2x80x9cset.xe2x80x9d If exposure occurs within the container, the relatively fast reactive nature of the adhesive will cause the adhesive solidify within the container, thus making the adhesive unusable.
Also, if the container does not prevent the release of the volatile component of the adhesive through the container wall, then xe2x80x9cbloomingxe2x80x9d may be seen on the outside of the container. xe2x80x9cBloomingxe2x80x9d is the formation of unsightly deposits on the exterior surface of the container.
In order to provide an effective barrier, containers for housing cyanoacrylate adhesives have been formed from a multi-layer composite structure. A traditional multi-layer material used for cyanoacrylate adhesive containers is a five layer structure comprising a layer of low-density polyethylene, a tie layer of an adhesive, a layer of EVOH, a tie layer of an adhesive, and a final layer of low to moderate-density polyethylene. Each the separate layers serves a particular purpose. First, the innermost layer of HDPE provides a moisture barrier to protect the adhesive and the moisture sensitive EVOH layer, and the tie layers provide a means of adhering the EVOH layer to the polyethylene layers. Without the tie layers to bond the other layers together, the container would easily delaminate and become susceptible to mechanical failure. This traditional structure also requires five separate extruders in order to form the multi-layer material for the container.
It is also desirable to have a container for cyanoacrylate adhesives which, while providing a sufficient barrier, is also readily squeezable by the human hand. The problem arises, however, when softer, more deformable materials are used for the container walls. These softer materials typically have an adverse reaction to the volatile component of the adhesive, which results in xe2x80x9cballooningxe2x80x9d of the container walls. Also, the more readily deformable material typically has a higher transmission rate of vapor, moisture, and oxygen, which, as stated above, can adversely effect the adhesive and the container.
Therefore, there still remains the need for a container for housing cyanoacrylate adhesives which will provide a vapor barrier, and a moisture barrier, and yet may be easily deformed by the human hand to enable accurate dispensing of a small quantity of adhesive.
The present invention provides a squeezable, multi-layer, structurally self-supporting container capable of dispensing a controlled amount of a liquid product. The container comprises an external layer of a polyolefin material, an internal layer formed of a polyolefin material, and an intermediate positioned between the external layer and the internal layer. The intermediate layer is formed of a barrier material blended with an adhesive resin.
The external layer and the internal layer are preferably polyethylene, polypropylene, or blends of polyethylene and polypropylene. Most preferably, the internal layer should be HDPE and the external layer are low-density polyethylene.
The barrier material making up a portion of the intermediate layer is preferably ethylene vinyl alcohol. The adhesive resin making up a portion of the intermediate layer is preferably an anhydride-modified polyolefin. Most preferably, the adhesive resin is an anhydride-modified polyethylene, an anhydride-modified high-density polyethylene, an anhydride-modified linear low-density polyethylene, an anhydride-modified low-density polyethylene, or an anhydride-modified polypropylene.
The advantages of the present invention are numerous. First, the reduction of the number of layers comprising the wall of the container decreases the number of steps required to manufacture the container itself. Also, the reduction of the number of layers allows the fabrication of a container which is structurally self-supporting under its own weight, while simultaneously being easily deformed by pressure applied by the human hand, thus enabling an accurate dispensing of a small amount of product. Additionally, the novel structure of the container provides an effective vapor and moisture barrier. With these and other advantages and features of the invention that may become apparent, the nature of the invention may be more clearly understood by reference to the following detailed description of the invention, the appended claims, and to the several drawings attached herein.